Just because you can doesn't mean you should. Anything worth doing is worth doing right. Don't use flouros except for clones and seedlings. If your going to use only one light for veg and flowering get an HPS Hortilex bulb with some blue spectrum to balance out the initial red spectrum that HPS offers. 400w can grow more than 2-3 plants. You should make your decision based on space set aside for garden. If your using a closet, go 250w because that closet is going to get hot. Get a book. Don't take this on blind. Research, research, research! Otherwise your wasting money.